Annotation of src/usr.bin/ssh/sshd.c, Revision 1.129
1.86 markus 1: /*
1.65 deraadt 2: * Author: Tatu Ylonen <ylo@cs.hut.fi>
3: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4: * All rights reserved
1.126 deraadt 5: * This program is the ssh daemon. It listens for connections from clients,
6: * and performs authentication, executes use commands or shell, and forwards
1.65 deraadt 7: * information to/from the application to the user client over an encrypted
1.126 deraadt 8: * connection. This can also handle forwarding of X11, TCP/IP, and
9: * authentication agent connections.
1.98 markus 10: *
1.126 deraadt 11: * As far as I am concerned, the code I have written for this software
12: * can be used freely for any purpose. Any derived versions of this
13: * software must be clearly marked as such, and if the derived work is
14: * incompatible with the protocol description in the RFC file, it must be
15: * called by a name other than "ssh" or "Secure Shell".
16: *
17: * SSH2 implementation:
18: *
19: * Copyright (c) 2000 Markus Friedl. All rights reserved.
20: *
21: * Redistribution and use in source and binary forms, with or without
22: * modification, are permitted provided that the following conditions
23: * are met:
24: * 1. Redistributions of source code must retain the above copyright
25: * notice, this list of conditions and the following disclaimer.
26: * 2. Redistributions in binary form must reproduce the above copyright
27: * notice, this list of conditions and the following disclaimer in the
28: * documentation and/or other materials provided with the distribution.
29: *
30: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
31: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
33: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
34: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
35: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
36: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
37: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
38: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
39: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.65 deraadt 40: */
1.1 deraadt 41:
42: #include "includes.h"
1.129 ! provos 43: RCSID("$OpenBSD: sshd.c,v 1.128 2000/09/17 15:38:59 markus Exp $");
1.1 deraadt 44:
45: #include "xmalloc.h"
46: #include "rsa.h"
47: #include "ssh.h"
48: #include "pty.h"
49: #include "packet.h"
50: #include "cipher.h"
51: #include "mpaux.h"
52: #include "servconf.h"
53: #include "uidswap.h"
1.33 markus 54: #include "compat.h"
1.96 markus 55: #include "buffer.h"
56:
1.98 markus 57: #include "ssh2.h"
1.104 markus 58: #include <openssl/dh.h>
59: #include <openssl/bn.h>
60: #include <openssl/hmac.h>
1.98 markus 61: #include "kex.h"
1.104 markus 62: #include <openssl/dsa.h>
63: #include <openssl/rsa.h>
1.96 markus 64: #include "key.h"
1.98 markus 65: #include "dsa.h"
1.129 ! provos 66: #include "dh.h"
1.96 markus 67:
68: #include "auth.h"
1.98 markus 69: #include "myproposal.h"
1.108 markus 70: #include "authfile.h"
1.1 deraadt 71:
72: #ifdef LIBWRAP
73: #include <tcpd.h>
74: #include <syslog.h>
75: int allow_severity = LOG_INFO;
76: int deny_severity = LOG_WARNING;
77: #endif /* LIBWRAP */
78:
79: #ifndef O_NOCTTY
80: #define O_NOCTTY 0
81: #endif
82:
83: /* Server configuration options. */
84: ServerOptions options;
85:
86: /* Name of the server configuration file. */
87: char *config_file_name = SERVER_CONFIG_FILE;
88:
1.105 markus 89: /*
1.75 markus 90: * Flag indicating whether IPv4 or IPv6. This can be set on the command line.
91: * Default value is AF_UNSPEC means both IPv4 and IPv6.
92: */
93: int IPv4or6 = AF_UNSPEC;
94:
1.65 deraadt 95: /*
96: * Debug mode flag. This can be set on the command line. If debug
97: * mode is enabled, extra debugging output will be sent to the system
98: * log, the daemon will not go to background, and will exit after processing
99: * the first connection.
100: */
1.1 deraadt 101: int debug_flag = 0;
102:
103: /* Flag indicating that the daemon is being started from inetd. */
104: int inetd_flag = 0;
105:
1.47 markus 106: /* debug goes to stderr unless inetd_flag is set */
107: int log_stderr = 0;
108:
1.1 deraadt 109: /* argv[0] without path. */
110: char *av0;
111:
112: /* Saved arguments to main(). */
113: char **saved_argv;
114:
1.66 markus 115: /*
1.75 markus 116: * The sockets that the server is listening; this is used in the SIGHUP
117: * signal handler.
1.66 markus 118: */
1.75 markus 119: #define MAX_LISTEN_SOCKS 16
120: int listen_socks[MAX_LISTEN_SOCKS];
121: int num_listen_socks = 0;
1.1 deraadt 122:
1.66 markus 123: /*
124: * the client's version string, passed by sshd2 in compat mode. if != NULL,
125: * sshd will skip the version-number exchange
126: */
1.61 markus 127: char *client_version_string = NULL;
1.96 markus 128: char *server_version_string = NULL;
1.1 deraadt 129:
1.66 markus 130: /*
131: * Any really sensitive data in the application is contained in this
132: * structure. The idea is that this structure could be locked into memory so
133: * that the pages do not get written into swap. However, there are some
134: * problems. The private key contains BIGNUMs, and we do not (in principle)
135: * have access to the internals of them, and locking just the structure is
136: * not very useful. Currently, memory locking is not implemented.
137: */
1.64 markus 138: struct {
1.108 markus 139: RSA *private_key; /* Private part of empheral server key. */
1.64 markus 140: RSA *host_key; /* Private part of host key. */
1.108 markus 141: Key *dsa_host_key; /* Private DSA host key. */
1.1 deraadt 142: } sensitive_data;
143:
1.66 markus 144: /*
145: * Flag indicating whether the current session key has been used. This flag
146: * is set whenever the key is used, and cleared when the key is regenerated.
147: */
1.1 deraadt 148: int key_used = 0;
149:
150: /* This is set to true when SIGHUP is received. */
151: int received_sighup = 0;
152:
153: /* Public side of the server key. This value is regenerated regularly with
154: the private key. */
1.2 provos 155: RSA *public_key;
1.1 deraadt 156:
1.96 markus 157: /* session identifier, used by RSA-auth */
158: unsigned char session_id[16];
159:
1.108 markus 160: /* same for ssh2 */
161: unsigned char *session_id2 = NULL;
162: int session_id2_len = 0;
163:
1.125 markus 164: /* record remote hostname or ip */
165: unsigned int utmp_len = MAXHOSTNAMELEN;
166:
1.1 deraadt 167: /* Prototypes for various functions defined later in this file. */
1.96 markus 168: void do_ssh1_kex();
1.98 markus 169: void do_ssh2_kex();
1.87 markus 170:
1.129 ! provos 171: void ssh_dh1_server(Kex *, Buffer *_kexinit, Buffer *);
! 172: void ssh_dhgex_server(Kex *, Buffer *_kexinit, Buffer *);
! 173:
1.87 markus 174: /*
1.75 markus 175: * Close all listening sockets
176: */
177: void
178: close_listen_socks(void)
179: {
180: int i;
181: for (i = 0; i < num_listen_socks; i++)
182: close(listen_socks[i]);
183: num_listen_socks = -1;
184: }
185:
186: /*
1.65 deraadt 187: * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
188: * the effect is to reread the configuration file (and to regenerate
189: * the server key).
190: */
1.105 markus 191: void
1.64 markus 192: sighup_handler(int sig)
1.1 deraadt 193: {
1.64 markus 194: received_sighup = 1;
195: signal(SIGHUP, sighup_handler);
1.1 deraadt 196: }
197:
1.65 deraadt 198: /*
199: * Called from the main program after receiving SIGHUP.
200: * Restarts the server.
201: */
1.105 markus 202: void
1.64 markus 203: sighup_restart()
1.1 deraadt 204: {
1.64 markus 205: log("Received SIGHUP; restarting.");
1.75 markus 206: close_listen_socks();
1.64 markus 207: execv(saved_argv[0], saved_argv);
208: log("RESTART FAILED: av0='%s', error: %s.", av0, strerror(errno));
209: exit(1);
1.1 deraadt 210: }
211:
1.65 deraadt 212: /*
213: * Generic signal handler for terminating signals in the master daemon.
214: * These close the listen socket; not closing it seems to cause "Address
215: * already in use" problems on some machines, which is inconvenient.
216: */
1.105 markus 217: void
1.64 markus 218: sigterm_handler(int sig)
1.1 deraadt 219: {
1.64 markus 220: log("Received signal %d; terminating.", sig);
1.75 markus 221: close_listen_socks();
1.113 markus 222: unlink(options.pid_file);
1.64 markus 223: exit(255);
1.1 deraadt 224: }
225:
1.65 deraadt 226: /*
227: * SIGCHLD handler. This is called whenever a child dies. This will then
228: * reap any zombies left by exited c.
229: */
1.105 markus 230: void
1.64 markus 231: main_sigchld_handler(int sig)
1.1 deraadt 232: {
1.64 markus 233: int save_errno = errno;
234: int status;
1.60 deraadt 235:
1.64 markus 236: while (waitpid(-1, &status, WNOHANG) > 0)
237: ;
1.60 deraadt 238:
1.64 markus 239: signal(SIGCHLD, main_sigchld_handler);
240: errno = save_errno;
1.1 deraadt 241: }
242:
1.65 deraadt 243: /*
244: * Signal handler for the alarm after the login grace period has expired.
245: */
1.105 markus 246: void
1.64 markus 247: grace_alarm_handler(int sig)
1.1 deraadt 248: {
1.64 markus 249: /* Close the connection. */
250: packet_close();
251:
252: /* Log error and exit. */
253: fatal("Timeout before authentication for %s.", get_remote_ipaddr());
1.62 markus 254: }
255:
1.65 deraadt 256: /*
257: * Signal handler for the key regeneration alarm. Note that this
258: * alarm only occurs in the daemon waiting for connections, and it does not
259: * do anything with the private key or random state before forking.
260: * Thus there should be no concurrency control/asynchronous execution
261: * problems.
262: */
1.108 markus 263: /* XXX do we really want this work to be done in a signal handler ? -m */
1.105 markus 264: void
1.64 markus 265: key_regeneration_alarm(int sig)
1.1 deraadt 266: {
1.64 markus 267: int save_errno = errno;
1.18 deraadt 268:
1.64 markus 269: /* Check if we should generate a new key. */
270: if (key_used) {
271: /* This should really be done in the background. */
272: log("Generating new %d bit RSA key.", options.server_key_bits);
273:
274: if (sensitive_data.private_key != NULL)
275: RSA_free(sensitive_data.private_key);
276: sensitive_data.private_key = RSA_new();
277:
278: if (public_key != NULL)
279: RSA_free(public_key);
280: public_key = RSA_new();
281:
282: rsa_generate_key(sensitive_data.private_key, public_key,
283: options.server_key_bits);
284: arc4random_stir();
285: key_used = 0;
286: log("RSA key generation complete.");
287: }
288: /* Reschedule the alarm. */
289: signal(SIGALRM, key_regeneration_alarm);
290: alarm(options.key_regeneration_time);
291: errno = save_errno;
1.98 markus 292: }
293:
1.96 markus 294: void
295: sshd_exchange_identification(int sock_in, int sock_out)
296: {
1.102 markus 297: int i, mismatch;
1.96 markus 298: int remote_major, remote_minor;
1.102 markus 299: int major, minor;
1.96 markus 300: char *s;
301: char buf[256]; /* Must not be larger than remote_version. */
302: char remote_version[256]; /* Must be at least as big as buf. */
303:
1.103 markus 304: if ((options.protocol & SSH_PROTO_1) &&
305: (options.protocol & SSH_PROTO_2)) {
1.102 markus 306: major = PROTOCOL_MAJOR_1;
307: minor = 99;
308: } else if (options.protocol & SSH_PROTO_2) {
309: major = PROTOCOL_MAJOR_2;
310: minor = PROTOCOL_MINOR_2;
311: } else {
312: major = PROTOCOL_MAJOR_1;
313: minor = PROTOCOL_MINOR_1;
314: }
315: snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
1.96 markus 316: server_version_string = xstrdup(buf);
317:
318: if (client_version_string == NULL) {
319: /* Send our protocol version identification. */
320: if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
321: != strlen(server_version_string)) {
322: log("Could not write ident string to %s.", get_remote_ipaddr());
323: fatal_cleanup();
324: }
325:
326: /* Read other side\'s version identification. */
327: for (i = 0; i < sizeof(buf) - 1; i++) {
1.119 markus 328: if (atomicio(read, sock_in, &buf[i], 1) != 1) {
1.96 markus 329: log("Did not receive ident string from %s.", get_remote_ipaddr());
330: fatal_cleanup();
331: }
332: if (buf[i] == '\r') {
333: buf[i] = '\n';
334: buf[i + 1] = 0;
335: continue;
336: }
337: if (buf[i] == '\n') {
338: /* buf[i] == '\n' */
339: buf[i + 1] = 0;
340: break;
341: }
342: }
343: buf[sizeof(buf) - 1] = 0;
344: client_version_string = xstrdup(buf);
345: }
346:
347: /*
348: * Check that the versions match. In future this might accept
349: * several versions and set appropriate flags to handle them.
350: */
351: if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
352: &remote_major, &remote_minor, remote_version) != 3) {
1.105 markus 353: s = "Protocol mismatch.\n";
1.96 markus 354: (void) atomicio(write, sock_out, s, strlen(s));
355: close(sock_in);
356: close(sock_out);
357: log("Bad protocol version identification '%.100s' from %s",
358: client_version_string, get_remote_ipaddr());
359: fatal_cleanup();
360: }
361: debug("Client protocol version %d.%d; client software version %.100s",
362: remote_major, remote_minor, remote_version);
363:
1.98 markus 364: compat_datafellows(remote_version);
365:
1.102 markus 366: mismatch = 0;
1.96 markus 367: switch(remote_major) {
368: case 1:
1.108 markus 369: if (remote_minor == 99) {
370: if (options.protocol & SSH_PROTO_2)
371: enable_compat20();
372: else
373: mismatch = 1;
374: break;
375: }
1.102 markus 376: if (!(options.protocol & SSH_PROTO_1)) {
377: mismatch = 1;
378: break;
379: }
1.96 markus 380: if (remote_minor < 3) {
1.121 provos 381: packet_disconnect("Your ssh version is too old and "
1.96 markus 382: "is no longer supported. Please install a newer version.");
383: } else if (remote_minor == 3) {
384: /* note that this disables agent-forwarding */
385: enable_compat13();
386: }
1.102 markus 387: break;
1.98 markus 388: case 2:
1.102 markus 389: if (options.protocol & SSH_PROTO_2) {
1.98 markus 390: enable_compat20();
391: break;
392: }
1.99 markus 393: /* FALLTHROUGH */
1.105 markus 394: default:
1.102 markus 395: mismatch = 1;
396: break;
397: }
398: chop(server_version_string);
399: chop(client_version_string);
400: debug("Local version string %.200s", server_version_string);
401:
402: if (mismatch) {
1.96 markus 403: s = "Protocol major versions differ.\n";
404: (void) atomicio(write, sock_out, s, strlen(s));
405: close(sock_in);
406: close(sock_out);
1.102 markus 407: log("Protocol major versions differ for %s: %.200s vs. %.200s",
408: get_remote_ipaddr(),
409: server_version_string, client_version_string);
1.96 markus 410: fatal_cleanup();
411: }
1.108 markus 412: if (compat20)
413: packet_set_ssh2_format();
414: }
415:
416:
417: void
418: destroy_sensitive_data(void)
419: {
420: /* Destroy the private and public keys. They will no longer be needed. */
1.117 djm 421: if (public_key)
422: RSA_free(public_key);
423: if (sensitive_data.private_key)
424: RSA_free(sensitive_data.private_key);
425: if (sensitive_data.host_key)
426: RSA_free(sensitive_data.host_key);
1.108 markus 427: if (sensitive_data.dsa_host_key != NULL)
428: key_free(sensitive_data.dsa_host_key);
1.96 markus 429: }
430:
1.124 markus 431: /*
432: * returns 1 if connection should be dropped, 0 otherwise.
433: * dropping starts at connection #max_startups_begin with a probability
434: * of (max_startups_rate/100). the probability increases linearly until
435: * all connections are dropped for startups > max_startups
436: */
437: int
438: drop_connection(int startups)
439: {
440: double p, r;
441:
442: if (startups < options.max_startups_begin)
443: return 0;
444: if (startups >= options.max_startups)
445: return 1;
446: if (options.max_startups_rate == 100)
447: return 1;
448:
449: p = 100 - options.max_startups_rate;
450: p *= startups - options.max_startups_begin;
451: p /= (double) (options.max_startups - options.max_startups_begin);
452: p += options.max_startups_rate;
453: p /= 100.0;
454: r = arc4random() / (double) UINT_MAX;
455:
456: debug("drop_connection: p %g, r %g", p, r);
457: return (r < p) ? 1 : 0;
458: }
459:
1.120 markus 460: int *startup_pipes = NULL; /* options.max_startup sized array of fd ints */
461: int startup_pipe; /* in child */
462:
1.65 deraadt 463: /*
464: * Main program for the daemon.
465: */
1.2 provos 466: int
467: main(int ac, char **av)
1.1 deraadt 468: {
1.64 markus 469: extern char *optarg;
470: extern int optind;
1.120 markus 471: int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
1.107 deraadt 472: pid_t pid;
1.75 markus 473: socklen_t fromlen;
1.110 markus 474: int silent = 0;
1.75 markus 475: fd_set *fdset;
476: struct sockaddr_storage from;
1.64 markus 477: const char *remote_ip;
478: int remote_port;
479: FILE *f;
480: struct linger linger;
1.75 markus 481: struct addrinfo *ai;
482: char ntop[NI_MAXHOST], strport[NI_MAXSERV];
483: int listen_sock, maxfd;
1.120 markus 484: int startup_p[2];
485: int startups = 0;
1.64 markus 486:
487: /* Save argv[0]. */
488: saved_argv = av;
489: if (strchr(av[0], '/'))
490: av0 = strrchr(av[0], '/') + 1;
491: else
492: av0 = av[0];
493:
494: /* Initialize configuration options to their default values. */
495: initialize_server_options(&options);
496:
497: /* Parse command-line arguments. */
1.125 markus 498: while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:diqQ46")) != EOF) {
1.64 markus 499: switch (opt) {
1.75 markus 500: case '4':
501: IPv4or6 = AF_INET;
502: break;
503: case '6':
504: IPv4or6 = AF_INET6;
505: break;
1.64 markus 506: case 'f':
507: config_file_name = optarg;
508: break;
509: case 'd':
1.127 markus 510: if (0 == debug_flag) {
511: debug_flag = 1;
512: options.log_level = SYSLOG_LEVEL_DEBUG1;
513: } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
514: options.log_level++;
515: } else {
516: fprintf(stderr, "Too high debugging level.\n");
517: exit(1);
518: }
1.64 markus 519: break;
520: case 'i':
521: inetd_flag = 1;
522: break;
523: case 'Q':
1.110 markus 524: silent = 1;
1.64 markus 525: break;
526: case 'q':
527: options.log_level = SYSLOG_LEVEL_QUIET;
528: break;
529: case 'b':
530: options.server_key_bits = atoi(optarg);
531: break;
532: case 'p':
1.75 markus 533: options.ports_from_cmdline = 1;
1.127 markus 534: if (options.num_ports >= MAX_PORTS) {
535: fprintf(stderr, "too many ports.\n");
536: exit(1);
537: }
1.75 markus 538: options.ports[options.num_ports++] = atoi(optarg);
1.64 markus 539: break;
540: case 'g':
541: options.login_grace_time = atoi(optarg);
542: break;
543: case 'k':
544: options.key_regeneration_time = atoi(optarg);
545: break;
546: case 'h':
547: options.host_key_file = optarg;
548: break;
549: case 'V':
550: client_version_string = optarg;
551: /* only makes sense with inetd_flag, i.e. no listen() */
552: inetd_flag = 1;
553: break;
1.125 markus 554: case 'u':
555: utmp_len = atoi(optarg);
556: break;
1.64 markus 557: case '?':
558: default:
559: fprintf(stderr, "sshd version %s\n", SSH_VERSION);
560: fprintf(stderr, "Usage: %s [options]\n", av0);
561: fprintf(stderr, "Options:\n");
1.66 markus 562: fprintf(stderr, " -f file Configuration file (default %s)\n", SERVER_CONFIG_FILE);
1.127 markus 563: fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n");
1.64 markus 564: fprintf(stderr, " -i Started from inetd\n");
565: fprintf(stderr, " -q Quiet (no logging)\n");
566: fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
567: fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
568: fprintf(stderr, " -g seconds Grace period for authentication (default: 300)\n");
569: fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
570: fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
1.75 markus 571: HOST_KEY_FILE);
1.125 markus 572: fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
1.75 markus 573: fprintf(stderr, " -4 Use IPv4 only\n");
574: fprintf(stderr, " -6 Use IPv6 only\n");
1.64 markus 575: exit(1);
576: }
577: }
578:
1.75 markus 579: /*
580: * Force logging to stderr until we have loaded the private host
581: * key (unless started from inetd)
582: */
583: log_init(av0,
584: options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
585: options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
1.110 markus 586: !silent && !inetd_flag);
1.75 markus 587:
1.64 markus 588: /* Read server configuration options from the configuration file. */
589: read_server_config(&options, config_file_name);
590:
591: /* Fill in default values for those options not explicitly set. */
592: fill_default_server_options(&options);
593:
594: /* Check that there are no remaining arguments. */
595: if (optind < ac) {
596: fprintf(stderr, "Extra argument %s.\n", av[optind]);
597: exit(1);
598: }
599:
600: debug("sshd version %.100s", SSH_VERSION);
601:
1.108 markus 602: sensitive_data.dsa_host_key = NULL;
603: sensitive_data.host_key = NULL;
604:
605: /* check if RSA support exists */
606: if ((options.protocol & SSH_PROTO_1) &&
607: rsa_alive() == 0) {
608: log("no RSA support in libssl and libcrypto. See ssl(8)");
609: log("Disabling protocol version 1");
610: options.protocol &= ~SSH_PROTO_1;
611: }
612: /* Load the RSA/DSA host key. It must have empty passphrase. */
613: if (options.protocol & SSH_PROTO_1) {
614: Key k;
615: sensitive_data.host_key = RSA_new();
616: k.type = KEY_RSA;
617: k.rsa = sensitive_data.host_key;
618: errno = 0;
1.109 markus 619: if (!load_private_key(options.host_key_file, "", &k, NULL)) {
1.108 markus 620: error("Could not load host key: %.200s: %.100s",
621: options.host_key_file, strerror(errno));
622: log("Disabling protocol version 1");
623: options.protocol &= ~SSH_PROTO_1;
624: }
625: k.rsa = NULL;
626: }
627: if (options.protocol & SSH_PROTO_2) {
628: sensitive_data.dsa_host_key = key_new(KEY_DSA);
1.115 markus 629: if (!load_private_key(options.host_dsa_key_file, "", sensitive_data.dsa_host_key, NULL)) {
630:
631: error("Could not load DSA host key: %.200s", options.host_dsa_key_file);
1.108 markus 632: log("Disabling protocol version 2");
633: options.protocol &= ~SSH_PROTO_2;
634: }
635: }
636: if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) {
1.110 markus 637: if (silent == 0)
638: fprintf(stderr, "sshd: no hostkeys available -- exiting.\n");
1.108 markus 639: log("sshd: no hostkeys available -- exiting.\n");
1.64 markus 640: exit(1);
641: }
642:
1.108 markus 643: /* Check certain values for sanity. */
644: if (options.protocol & SSH_PROTO_1) {
645: if (options.server_key_bits < 512 ||
646: options.server_key_bits > 32768) {
647: fprintf(stderr, "Bad server key size.\n");
648: exit(1);
649: }
650: /*
651: * Check that server and host key lengths differ sufficiently. This
652: * is necessary to make double encryption work with rsaref. Oh, I
653: * hate software patents. I dont know if this can go? Niels
654: */
655: if (options.server_key_bits >
656: BN_num_bits(sensitive_data.host_key->n) - SSH_KEY_BITS_RESERVED &&
657: options.server_key_bits <
658: BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
659: options.server_key_bits =
660: BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED;
661: debug("Forcing server key to %d bits to make it differ from host key.",
662: options.server_key_bits);
663: }
664: }
665:
666: /* Initialize the log (it is reinitialized below in case we forked). */
1.64 markus 667: if (debug_flag && !inetd_flag)
668: log_stderr = 1;
669: log_init(av0, options.log_level, options.log_facility, log_stderr);
670:
1.108 markus 671: /*
672: * If not in debugging mode, and not started from inetd, disconnect
673: * from the controlling terminal, and fork. The original process
674: * exits.
675: */
1.64 markus 676: if (!debug_flag && !inetd_flag) {
1.1 deraadt 677: #ifdef TIOCNOTTY
1.64 markus 678: int fd;
1.1 deraadt 679: #endif /* TIOCNOTTY */
1.64 markus 680: if (daemon(0, 0) < 0)
681: fatal("daemon() failed: %.200s", strerror(errno));
682:
683: /* Disconnect from the controlling tty. */
1.1 deraadt 684: #ifdef TIOCNOTTY
1.64 markus 685: fd = open("/dev/tty", O_RDWR | O_NOCTTY);
686: if (fd >= 0) {
687: (void) ioctl(fd, TIOCNOTTY, NULL);
688: close(fd);
689: }
690: #endif /* TIOCNOTTY */
691: }
692: /* Reinitialize the log (because of the fork above). */
693: log_init(av0, options.log_level, options.log_facility, log_stderr);
694:
695: /* Do not display messages to stdout in RSA code. */
696: rsa_set_verbose(0);
697:
698: /* Initialize the random number generator. */
699: arc4random_stir();
700:
701: /* Chdir to the root directory so that the current disk can be
702: unmounted if desired. */
703: chdir("/");
704:
705: /* Start listening for a socket, unless started from inetd. */
706: if (inetd_flag) {
707: int s1, s2;
708: s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
709: s2 = dup(s1);
710: sock_in = dup(0);
711: sock_out = dup(1);
1.123 djm 712: startup_pipe = -1;
1.108 markus 713: /*
714: * We intentionally do not close the descriptors 0, 1, and 2
715: * as our code for setting the descriptors won\'t work if
716: * ttyfd happens to be one of those.
717: */
1.64 markus 718: debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
719:
1.108 markus 720: if (options.protocol & SSH_PROTO_1) {
721: public_key = RSA_new();
722: sensitive_data.private_key = RSA_new();
723: log("Generating %d bit RSA key.", options.server_key_bits);
724: rsa_generate_key(sensitive_data.private_key, public_key,
725: options.server_key_bits);
726: arc4random_stir();
727: log("RSA key generation complete.");
728: }
1.64 markus 729: } else {
1.75 markus 730: for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
731: if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
732: continue;
733: if (num_listen_socks >= MAX_LISTEN_SOCKS)
734: fatal("Too many listen sockets. "
735: "Enlarge MAX_LISTEN_SOCKS");
736: if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
737: ntop, sizeof(ntop), strport, sizeof(strport),
738: NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
739: error("getnameinfo failed");
740: continue;
741: }
742: /* Create socket for listening. */
743: listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
744: if (listen_sock < 0) {
745: /* kernel may not support ipv6 */
746: verbose("socket: %.100s", strerror(errno));
747: continue;
748: }
749: if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
750: error("listen_sock O_NONBLOCK: %s", strerror(errno));
751: close(listen_sock);
752: continue;
753: }
754: /*
755: * Set socket options. We try to make the port
756: * reusable and have it close as fast as possible
757: * without waiting in unnecessary wait states on
758: * close.
759: */
760: setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
761: (void *) &on, sizeof(on));
762: linger.l_onoff = 1;
763: linger.l_linger = 5;
764: setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
765: (void *) &linger, sizeof(linger));
766:
767: debug("Bind to port %s on %s.", strport, ntop);
768:
769: /* Bind the socket to the desired port. */
770: if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
771: error("Bind to port %s on %s failed: %.200s.",
772: strport, ntop, strerror(errno));
773: close(listen_sock);
774: continue;
775: }
776: listen_socks[num_listen_socks] = listen_sock;
777: num_listen_socks++;
778:
779: /* Start listening on the port. */
780: log("Server listening on %s port %s.", ntop, strport);
781: if (listen(listen_sock, 5) < 0)
782: fatal("listen: %.100s", strerror(errno));
783:
1.64 markus 784: }
1.75 markus 785: freeaddrinfo(options.listen_addrs);
786:
787: if (!num_listen_socks)
788: fatal("Cannot bind any address.");
789:
1.64 markus 790: if (!debug_flag) {
1.66 markus 791: /*
792: * Record our pid in /etc/sshd_pid to make it easier
793: * to kill the correct sshd. We don\'t want to do
794: * this before the bind above because the bind will
795: * fail if there already is a daemon, and this will
796: * overwrite any old pid in the file.
797: */
1.112 markus 798: f = fopen(options.pid_file, "w");
1.64 markus 799: if (f) {
800: fprintf(f, "%u\n", (unsigned int) getpid());
801: fclose(f);
802: }
803: }
1.108 markus 804: if (options.protocol & SSH_PROTO_1) {
805: public_key = RSA_new();
806: sensitive_data.private_key = RSA_new();
807:
808: log("Generating %d bit RSA key.", options.server_key_bits);
809: rsa_generate_key(sensitive_data.private_key, public_key,
810: options.server_key_bits);
811: arc4random_stir();
812: log("RSA key generation complete.");
1.64 markus 813:
1.108 markus 814: /* Schedule server key regeneration alarm. */
815: signal(SIGALRM, key_regeneration_alarm);
816: alarm(options.key_regeneration_time);
817: }
1.64 markus 818:
819: /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
820: signal(SIGHUP, sighup_handler);
1.120 markus 821:
1.64 markus 822: signal(SIGTERM, sigterm_handler);
823: signal(SIGQUIT, sigterm_handler);
824:
825: /* Arrange SIGCHLD to be caught. */
826: signal(SIGCHLD, main_sigchld_handler);
827:
1.75 markus 828: /* setup fd set for listen */
1.120 markus 829: fdset = NULL;
1.75 markus 830: maxfd = 0;
831: for (i = 0; i < num_listen_socks; i++)
832: if (listen_socks[i] > maxfd)
833: maxfd = listen_socks[i];
1.120 markus 834: /* pipes connected to unauthenticated childs */
835: startup_pipes = xmalloc(options.max_startups * sizeof(int));
836: for (i = 0; i < options.max_startups; i++)
837: startup_pipes[i] = -1;
1.75 markus 838:
1.66 markus 839: /*
840: * Stay listening for connections until the system crashes or
841: * the daemon is killed with a signal.
842: */
1.64 markus 843: for (;;) {
844: if (received_sighup)
845: sighup_restart();
1.120 markus 846: if (fdset != NULL)
847: xfree(fdset);
848: fdsetsz = howmany(maxfd, NFDBITS) * sizeof(fd_mask);
849: fdset = (fd_set *)xmalloc(fdsetsz);
1.75 markus 850: memset(fdset, 0, fdsetsz);
1.120 markus 851:
1.75 markus 852: for (i = 0; i < num_listen_socks; i++)
853: FD_SET(listen_socks[i], fdset);
1.120 markus 854: for (i = 0; i < options.max_startups; i++)
855: if (startup_pipes[i] != -1)
856: FD_SET(startup_pipes[i], fdset);
857:
858: /* Wait in select until there is a connection. */
1.75 markus 859: if (select(maxfd + 1, fdset, NULL, NULL, NULL) < 0) {
860: if (errno != EINTR)
861: error("select: %.100s", strerror(errno));
862: continue;
863: }
1.120 markus 864: for (i = 0; i < options.max_startups; i++)
865: if (startup_pipes[i] != -1 &&
866: FD_ISSET(startup_pipes[i], fdset)) {
867: /*
868: * the read end of the pipe is ready
869: * if the child has closed the pipe
870: * after successfull authentication
871: * or if the child has died
872: */
873: close(startup_pipes[i]);
874: startup_pipes[i] = -1;
875: startups--;
876: }
1.75 markus 877: for (i = 0; i < num_listen_socks; i++) {
878: if (!FD_ISSET(listen_socks[i], fdset))
1.70 provos 879: continue;
1.120 markus 880: fromlen = sizeof(from);
881: newsock = accept(listen_socks[i], (struct sockaddr *)&from,
882: &fromlen);
883: if (newsock < 0) {
884: if (errno != EINTR && errno != EWOULDBLOCK)
885: error("accept: %.100s", strerror(errno));
886: continue;
887: }
888: if (fcntl(newsock, F_SETFL, 0) < 0) {
889: error("newsock del O_NONBLOCK: %s", strerror(errno));
890: continue;
891: }
1.124 markus 892: if (drop_connection(startups) == 1) {
893: debug("drop connection #%d", startups);
1.120 markus 894: close(newsock);
895: continue;
896: }
897: if (pipe(startup_p) == -1) {
898: close(newsock);
899: continue;
900: }
901:
902: for (j = 0; j < options.max_startups; j++)
903: if (startup_pipes[j] == -1) {
904: startup_pipes[j] = startup_p[0];
905: if (maxfd < startup_p[0])
906: maxfd = startup_p[0];
907: startups++;
908: break;
909: }
910:
1.66 markus 911: /*
1.120 markus 912: * Got connection. Fork a child to handle it, unless
913: * we are in debugging mode.
1.66 markus 914: */
1.120 markus 915: if (debug_flag) {
1.66 markus 916: /*
1.120 markus 917: * In debugging mode. Close the listening
918: * socket, and start processing the
919: * connection without forking.
1.66 markus 920: */
1.120 markus 921: debug("Server will not fork when running in debugging mode.");
1.75 markus 922: close_listen_socks();
1.64 markus 923: sock_in = newsock;
924: sock_out = newsock;
1.122 deraadt 925: startup_pipe = -1;
1.120 markus 926: pid = getpid();
1.64 markus 927: break;
1.120 markus 928: } else {
929: /*
930: * Normal production daemon. Fork, and have
931: * the child process the connection. The
932: * parent continues listening.
933: */
934: if ((pid = fork()) == 0) {
935: /*
936: * Child. Close the listening and max_startup
937: * sockets. Start using the accepted socket.
938: * Reinitialize logging (since our pid has
939: * changed). We break out of the loop to handle
940: * the connection.
941: */
942: startup_pipe = startup_p[1];
943: for (j = 0; j < options.max_startups; j++)
944: if (startup_pipes[j] != -1)
945: close(startup_pipes[j]);
946: close_listen_socks();
947: sock_in = newsock;
948: sock_out = newsock;
949: log_init(av0, options.log_level, options.log_facility, log_stderr);
950: break;
951: }
1.64 markus 952: }
953:
1.120 markus 954: /* Parent. Stay in the loop. */
955: if (pid < 0)
956: error("fork: %.100s", strerror(errno));
957: else
958: debug("Forked child %d.", pid);
959:
960: close(startup_p[1]);
1.1 deraadt 961:
1.120 markus 962: /* Mark that the key has been used (it was "given" to the child). */
963: key_used = 1;
1.1 deraadt 964:
1.120 markus 965: arc4random_stir();
1.1 deraadt 966:
1.120 markus 967: /* Close the new socket (the child is now taking care of it). */
968: close(newsock);
969: }
1.75 markus 970: /* child process check (or debug mode) */
971: if (num_listen_socks < 0)
972: break;
1.64 markus 973: }
1.1 deraadt 974: }
975:
1.64 markus 976: /* This is the child processing a new connection. */
977:
1.66 markus 978: /*
979: * Disable the key regeneration alarm. We will not regenerate the
980: * key since we are no longer in a position to give it to anyone. We
981: * will not restart on SIGHUP since it no longer makes sense.
982: */
1.64 markus 983: alarm(0);
984: signal(SIGALRM, SIG_DFL);
985: signal(SIGHUP, SIG_DFL);
986: signal(SIGTERM, SIG_DFL);
987: signal(SIGQUIT, SIG_DFL);
988: signal(SIGCHLD, SIG_DFL);
989:
1.66 markus 990: /*
991: * Set socket options for the connection. We want the socket to
992: * close as fast as possible without waiting for anything. If the
993: * connection is not a socket, these will do nothing.
994: */
995: /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1.64 markus 996: linger.l_onoff = 1;
997: linger.l_linger = 5;
998: setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
999:
1.66 markus 1000: /*
1001: * Register our connection. This turns encryption off because we do
1002: * not have a key.
1003: */
1.64 markus 1004: packet_set_connection(sock_in, sock_out);
1.1 deraadt 1005:
1.64 markus 1006: remote_port = get_remote_port();
1007: remote_ip = get_remote_ipaddr();
1.52 markus 1008:
1.64 markus 1009: /* Check whether logins are denied from this host. */
1.37 dugsong 1010: #ifdef LIBWRAP
1.75 markus 1011: /* XXX LIBWRAP noes not know about IPv6 */
1.64 markus 1012: {
1013: struct request_info req;
1.37 dugsong 1014:
1.64 markus 1015: request_init(&req, RQ_DAEMON, av0, RQ_FILE, sock_in, NULL);
1016: fromhost(&req);
1.37 dugsong 1017:
1.64 markus 1018: if (!hosts_access(&req)) {
1019: close(sock_in);
1020: close(sock_out);
1021: refuse(&req);
1022: }
1.75 markus 1023: /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
1.64 markus 1024: }
1.75 markus 1025: #endif /* LIBWRAP */
1.64 markus 1026: /* Log the connection. */
1027: verbose("Connection from %.500s port %d", remote_ip, remote_port);
1.1 deraadt 1028:
1.66 markus 1029: /*
1030: * We don\'t want to listen forever unless the other side
1031: * successfully authenticates itself. So we set up an alarm which is
1032: * cleared after successful authentication. A limit of zero
1033: * indicates no limit. Note that we don\'t set the alarm in debugging
1034: * mode; it is just annoying to have the server exit just when you
1035: * are about to discover the bug.
1036: */
1.64 markus 1037: signal(SIGALRM, grace_alarm_handler);
1038: if (!debug_flag)
1039: alarm(options.login_grace_time);
1040:
1.96 markus 1041: sshd_exchange_identification(sock_in, sock_out);
1.66 markus 1042: /*
1043: * Check that the connection comes from a privileged port. Rhosts-
1044: * and Rhosts-RSA-Authentication only make sense from priviledged
1045: * programs. Of course, if the intruder has root access on his local
1046: * machine, he can connect from any port. So do not use these
1047: * authentication methods from machines that you do not trust.
1048: */
1.64 markus 1049: if (remote_port >= IPPORT_RESERVED ||
1050: remote_port < IPPORT_RESERVED / 2) {
1051: options.rhosts_authentication = 0;
1052: options.rhosts_rsa_authentication = 0;
1053: }
1.76 markus 1054: #ifdef KRB4
1055: if (!packet_connection_is_ipv4() &&
1056: options.kerberos_authentication) {
1057: debug("Kerberos Authentication disabled, only available for IPv4.");
1058: options.kerberos_authentication = 0;
1059: }
1060: #endif /* KRB4 */
1061:
1.64 markus 1062: packet_set_nonblocking();
1.1 deraadt 1063:
1.77 markus 1064: /* perform the key exchange */
1065: /* authenticate user and start session */
1.98 markus 1066: if (compat20) {
1067: do_ssh2_kex();
1068: do_authentication2();
1069: } else {
1070: do_ssh1_kex();
1071: do_authentication();
1072: }
1.1 deraadt 1073:
1074: #ifdef KRB4
1.64 markus 1075: /* Cleanup user's ticket cache file. */
1076: if (options.kerberos_ticket_cleanup)
1077: (void) dest_tkt();
1.1 deraadt 1078: #endif /* KRB4 */
1079:
1.64 markus 1080: /* The connection has been terminated. */
1081: verbose("Closing connection to %.100s", remote_ip);
1082: packet_close();
1083: exit(0);
1.1 deraadt 1084: }
1085:
1.65 deraadt 1086: /*
1.77 markus 1087: * SSH1 key exchange
1.65 deraadt 1088: */
1.52 markus 1089: void
1.96 markus 1090: do_ssh1_kex()
1.1 deraadt 1091: {
1.64 markus 1092: int i, len;
1.77 markus 1093: int plen, slen;
1.64 markus 1094: BIGNUM *session_key_int;
1095: unsigned char session_key[SSH_SESSION_KEY_LENGTH];
1.77 markus 1096: unsigned char cookie[8];
1.64 markus 1097: unsigned int cipher_type, auth_mask, protocol_flags;
1098: u_int32_t rand = 0;
1099:
1.66 markus 1100: /*
1101: * Generate check bytes that the client must send back in the user
1102: * packet in order for it to be accepted; this is used to defy ip
1103: * spoofing attacks. Note that this only works against somebody
1104: * doing IP spoofing from a remote machine; any machine on the local
1105: * network can still see outgoing packets and catch the random
1106: * cookie. This only affects rhosts authentication, and this is one
1107: * of the reasons why it is inherently insecure.
1108: */
1.64 markus 1109: for (i = 0; i < 8; i++) {
1110: if (i % 4 == 0)
1111: rand = arc4random();
1.77 markus 1112: cookie[i] = rand & 0xff;
1.64 markus 1113: rand >>= 8;
1114: }
1115:
1.66 markus 1116: /*
1117: * Send our public key. We include in the packet 64 bits of random
1118: * data that must be matched in the reply in order to prevent IP
1119: * spoofing.
1120: */
1.64 markus 1121: packet_start(SSH_SMSG_PUBLIC_KEY);
1122: for (i = 0; i < 8; i++)
1.77 markus 1123: packet_put_char(cookie[i]);
1.64 markus 1124:
1125: /* Store our public server RSA key. */
1126: packet_put_int(BN_num_bits(public_key->n));
1127: packet_put_bignum(public_key->e);
1128: packet_put_bignum(public_key->n);
1129:
1130: /* Store our public host RSA key. */
1131: packet_put_int(BN_num_bits(sensitive_data.host_key->n));
1132: packet_put_bignum(sensitive_data.host_key->e);
1133: packet_put_bignum(sensitive_data.host_key->n);
1134:
1135: /* Put protocol flags. */
1136: packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1137:
1138: /* Declare which ciphers we support. */
1.97 markus 1139: packet_put_int(cipher_mask1());
1.64 markus 1140:
1141: /* Declare supported authentication types. */
1142: auth_mask = 0;
1143: if (options.rhosts_authentication)
1144: auth_mask |= 1 << SSH_AUTH_RHOSTS;
1145: if (options.rhosts_rsa_authentication)
1146: auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1147: if (options.rsa_authentication)
1148: auth_mask |= 1 << SSH_AUTH_RSA;
1.1 deraadt 1149: #ifdef KRB4
1.64 markus 1150: if (options.kerberos_authentication)
1151: auth_mask |= 1 << SSH_AUTH_KERBEROS;
1.1 deraadt 1152: #endif
1.5 dugsong 1153: #ifdef AFS
1.64 markus 1154: if (options.kerberos_tgt_passing)
1155: auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1156: if (options.afs_token_passing)
1157: auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1.1 deraadt 1158: #endif
1.63 markus 1159: #ifdef SKEY
1.64 markus 1160: if (options.skey_authentication == 1)
1161: auth_mask |= 1 << SSH_AUTH_TIS;
1.63 markus 1162: #endif
1.64 markus 1163: if (options.password_authentication)
1164: auth_mask |= 1 << SSH_AUTH_PASSWORD;
1165: packet_put_int(auth_mask);
1166:
1167: /* Send the packet and wait for it to be sent. */
1168: packet_send();
1169: packet_write_wait();
1170:
1171: debug("Sent %d bit public key and %d bit host key.",
1172: BN_num_bits(public_key->n), BN_num_bits(sensitive_data.host_key->n));
1173:
1174: /* Read clients reply (cipher type and session key). */
1175: packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1176:
1.69 markus 1177: /* Get cipher type and check whether we accept this. */
1.64 markus 1178: cipher_type = packet_get_char();
1.69 markus 1179:
1.105 markus 1180: if (!(cipher_mask() & (1 << cipher_type)))
1.69 markus 1181: packet_disconnect("Warning: client selects unsupported cipher.");
1.64 markus 1182:
1183: /* Get check bytes from the packet. These must match those we
1184: sent earlier with the public key packet. */
1185: for (i = 0; i < 8; i++)
1.77 markus 1186: if (cookie[i] != packet_get_char())
1.64 markus 1187: packet_disconnect("IP Spoofing check bytes do not match.");
1188:
1189: debug("Encryption type: %.200s", cipher_name(cipher_type));
1190:
1191: /* Get the encrypted integer. */
1192: session_key_int = BN_new();
1193: packet_get_bignum(session_key_int, &slen);
1194:
1195: protocol_flags = packet_get_int();
1196: packet_set_protocol_flags(protocol_flags);
1197:
1198: packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1199:
1.66 markus 1200: /*
1201: * Decrypt it using our private server key and private host key (key
1202: * with larger modulus first).
1203: */
1.64 markus 1204: if (BN_cmp(sensitive_data.private_key->n, sensitive_data.host_key->n) > 0) {
1205: /* Private key has bigger modulus. */
1206: if (BN_num_bits(sensitive_data.private_key->n) <
1207: BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
1208: fatal("do_connection: %s: private_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1209: get_remote_ipaddr(),
1210: BN_num_bits(sensitive_data.private_key->n),
1211: BN_num_bits(sensitive_data.host_key->n),
1212: SSH_KEY_BITS_RESERVED);
1213: }
1214: rsa_private_decrypt(session_key_int, session_key_int,
1215: sensitive_data.private_key);
1216: rsa_private_decrypt(session_key_int, session_key_int,
1217: sensitive_data.host_key);
1218: } else {
1219: /* Host key has bigger modulus (or they are equal). */
1220: if (BN_num_bits(sensitive_data.host_key->n) <
1221: BN_num_bits(sensitive_data.private_key->n) + SSH_KEY_BITS_RESERVED) {
1222: fatal("do_connection: %s: host_key %d < private_key %d + SSH_KEY_BITS_RESERVED %d",
1223: get_remote_ipaddr(),
1224: BN_num_bits(sensitive_data.host_key->n),
1225: BN_num_bits(sensitive_data.private_key->n),
1226: SSH_KEY_BITS_RESERVED);
1227: }
1228: rsa_private_decrypt(session_key_int, session_key_int,
1229: sensitive_data.host_key);
1230: rsa_private_decrypt(session_key_int, session_key_int,
1231: sensitive_data.private_key);
1232: }
1233:
1.77 markus 1234: compute_session_id(session_id, cookie,
1.64 markus 1235: sensitive_data.host_key->n,
1236: sensitive_data.private_key->n);
1237:
1.77 markus 1238: /* Destroy the private and public keys. They will no longer be needed. */
1.108 markus 1239: destroy_sensitive_data();
1.77 markus 1240:
1.66 markus 1241: /*
1242: * Extract session key from the decrypted integer. The key is in the
1243: * least significant 256 bits of the integer; the first byte of the
1244: * key is in the highest bits.
1245: */
1.64 markus 1246: BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1247: len = BN_num_bytes(session_key_int);
1248: if (len < 0 || len > sizeof(session_key))
1249: fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
1250: get_remote_ipaddr(),
1251: len, sizeof(session_key));
1252: memset(session_key, 0, sizeof(session_key));
1253: BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
1254:
1.77 markus 1255: /* Destroy the decrypted integer. It is no longer needed. */
1256: BN_clear_free(session_key_int);
1257:
1.64 markus 1258: /* Xor the first 16 bytes of the session key with the session id. */
1259: for (i = 0; i < 16; i++)
1260: session_key[i] ^= session_id[i];
1261:
1262: /* Set the session key. From this on all communications will be encrypted. */
1263: packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1264:
1265: /* Destroy our copy of the session key. It is no longer needed. */
1266: memset(session_key, 0, sizeof(session_key));
1267:
1268: debug("Received session key; encryption turned on.");
1269:
1270: /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1271: packet_start(SSH_SMSG_SUCCESS);
1272: packet_send();
1273: packet_write_wait();
1.98 markus 1274: }
1275:
1276: /*
1277: * SSH2 key exchange: diffie-hellman-group1-sha1
1278: */
1279: void
1280: do_ssh2_kex()
1281: {
1282: Buffer *server_kexinit;
1283: Buffer *client_kexinit;
1.129 ! provos 1284: int payload_len;
1.98 markus 1285: int i;
1286: Kex *kex;
1287: char *cprop[PROPOSAL_MAX];
1288:
1289: /* KEXINIT */
1.102 markus 1290:
1291: if (options.ciphers != NULL) {
1.105 markus 1292: myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1.102 markus 1293: myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1294: }
1.118 markus 1295: server_kexinit = kex_init(myproposal);
1.98 markus 1296: client_kexinit = xmalloc(sizeof(*client_kexinit));
1297: buffer_init(client_kexinit);
1298:
1.118 markus 1299: /* algorithm negotiation */
1300: kex_exchange_kexinit(server_kexinit, client_kexinit, cprop);
1301: kex = kex_choose_conf(cprop, myproposal, 1);
1302: for (i = 0; i < PROPOSAL_MAX; i++)
1303: xfree(cprop[i]);
1.98 markus 1304:
1.129 ! provos 1305: switch (kex->kex_type) {
! 1306: case DH_GRP1_SHA1:
! 1307: ssh_dh1_server(kex, client_kexinit, server_kexinit);
! 1308: break;
! 1309: case DH_GEX_SHA1:
! 1310: ssh_dhgex_server(kex, client_kexinit, server_kexinit);
! 1311: break;
! 1312: default:
! 1313: fatal("Unsupported key exchange %d", kex->kex_type);
! 1314: }
! 1315:
! 1316: debug("send SSH2_MSG_NEWKEYS.");
! 1317: packet_start(SSH2_MSG_NEWKEYS);
! 1318: packet_send();
! 1319: packet_write_wait();
! 1320: debug("done: send SSH2_MSG_NEWKEYS.");
! 1321:
! 1322: debug("Wait SSH2_MSG_NEWKEYS.");
! 1323: packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS);
! 1324: debug("GOT SSH2_MSG_NEWKEYS.");
! 1325:
! 1326: #ifdef DEBUG_KEXDH
! 1327: /* send 1st encrypted/maced/compressed message */
! 1328: packet_start(SSH2_MSG_IGNORE);
! 1329: packet_put_cstring("markus");
! 1330: packet_send();
! 1331: packet_write_wait();
! 1332: #endif
! 1333:
! 1334: debug("done: KEX2.");
! 1335: }
! 1336:
! 1337: /*
! 1338: * SSH2 key exchange
! 1339: */
! 1340:
! 1341: /* diffie-hellman-group1-sha1 */
! 1342:
! 1343: void
! 1344: ssh_dh1_server(Kex *kex, Buffer *client_kexinit, Buffer *server_kexinit)
! 1345: {
! 1346: int payload_len, dlen;
! 1347: int slen;
! 1348: unsigned char *signature = NULL;
! 1349: unsigned char *server_host_key_blob = NULL;
! 1350: unsigned int sbloblen;
! 1351: unsigned int klen, kout;
! 1352: unsigned char *kbuf;
! 1353: unsigned char *hash;
! 1354: BIGNUM *shared_secret = 0;
! 1355: DH *dh;
! 1356: BIGNUM *dh_client_pub = 0;
! 1357:
1.98 markus 1358: /* KEXDH */
1359: debug("Wait SSH2_MSG_KEXDH_INIT.");
1360: packet_read_expect(&payload_len, SSH2_MSG_KEXDH_INIT);
1361:
1362: /* key, cert */
1363: dh_client_pub = BN_new();
1364: if (dh_client_pub == NULL)
1365: fatal("dh_client_pub == NULL");
1366: packet_get_bignum2(dh_client_pub, &dlen);
1367:
1368: #ifdef DEBUG_KEXDH
1369: fprintf(stderr, "\ndh_client_pub= ");
1.128 markus 1370: BN_print_fp(stderr, dh_client_pub);
1.98 markus 1371: fprintf(stderr, "\n");
1372: debug("bits %d", BN_num_bits(dh_client_pub));
1373: #endif
1374:
1375: /* generate DH key */
1.101 markus 1376: dh = dh_new_group1(); /* XXX depends on 'kex' */
1.98 markus 1377:
1378: #ifdef DEBUG_KEXDH
1379: fprintf(stderr, "\np= ");
1.128 markus 1380: BN_print_fp(stderr, dh->p);
1.98 markus 1381: fprintf(stderr, "\ng= ");
1.128 markus 1382: bn_print(dh->g);
1.98 markus 1383: fprintf(stderr, "\npub= ");
1.128 markus 1384: BN_print_fp(stderr, dh->pub_key);
1.98 markus 1385: fprintf(stderr, "\n");
1.128 markus 1386: DHparams_print_fp(stderr, dh);
1.98 markus 1387: #endif
1.101 markus 1388: if (!dh_pub_is_valid(dh, dh_client_pub))
1389: packet_disconnect("bad client public DH value");
1.98 markus 1390:
1391: klen = DH_size(dh);
1392: kbuf = xmalloc(klen);
1393: kout = DH_compute_key(kbuf, dh_client_pub, dh);
1394:
1395: #ifdef DEBUG_KEXDH
1396: debug("shared secret: len %d/%d", klen, kout);
1397: fprintf(stderr, "shared secret == ");
1398: for (i = 0; i< kout; i++)
1399: fprintf(stderr, "%02x", (kbuf[i])&0xff);
1400: fprintf(stderr, "\n");
1401: #endif
1402: shared_secret = BN_new();
1403:
1404: BN_bin2bn(kbuf, kout, shared_secret);
1405: memset(kbuf, 0, klen);
1406: xfree(kbuf);
1407:
1.111 markus 1408: /* XXX precompute? */
1.129 ! provos 1409: dsa_make_key_blob(sensitive_data.dsa_host_key,
! 1410: &server_host_key_blob, &sbloblen);
1.98 markus 1411:
1412: /* calc H */ /* XXX depends on 'kex' */
1413: hash = kex_hash(
1414: client_version_string,
1415: server_version_string,
1416: buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1417: buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1418: (char *)server_host_key_blob, sbloblen,
1419: dh_client_pub,
1420: dh->pub_key,
1421: shared_secret
1422: );
1423: buffer_free(client_kexinit);
1424: buffer_free(server_kexinit);
1425: xfree(client_kexinit);
1426: xfree(server_kexinit);
1427: #ifdef DEBUG_KEXDH
1.105 markus 1428: fprintf(stderr, "hash == ");
1429: for (i = 0; i< 20; i++)
1430: fprintf(stderr, "%02x", (hash[i])&0xff);
1431: fprintf(stderr, "\n");
1.98 markus 1432: #endif
1.108 markus 1433: /* save session id := H */
1434: /* XXX hashlen depends on KEX */
1435: session_id2_len = 20;
1436: session_id2 = xmalloc(session_id2_len);
1437: memcpy(session_id2, hash, session_id2_len);
1438:
1.98 markus 1439: /* sign H */
1.108 markus 1440: /* XXX hashlen depends on KEX */
1441: dsa_sign(sensitive_data.dsa_host_key, &signature, &slen, hash, 20);
1442:
1443: destroy_sensitive_data();
1.98 markus 1444:
1445: /* send server hostkey, DH pubkey 'f' and singed H */
1446: packet_start(SSH2_MSG_KEXDH_REPLY);
1447: packet_put_string((char *)server_host_key_blob, sbloblen);
1.114 markus 1448: packet_put_bignum2(dh->pub_key); /* f */
1.98 markus 1449: packet_put_string((char *)signature, slen);
1450: packet_send();
1.106 markus 1451: xfree(signature);
1.111 markus 1452: xfree(server_host_key_blob);
1.98 markus 1453: packet_write_wait();
1454:
1455: kex_derive_keys(kex, hash, shared_secret);
1456: packet_set_kex(kex);
1457:
1458: /* have keys, free DH */
1459: DH_free(dh);
1.129 ! provos 1460: }
! 1461:
! 1462: /* diffie-hellman-group-exchange-sha1 */
1.98 markus 1463:
1.129 ! provos 1464: void
! 1465: ssh_dhgex_server(Kex *kex, Buffer *client_kexinit, Buffer *server_kexinit)
! 1466: {
! 1467: int payload_len, dlen;
! 1468: int slen, nbits;
! 1469: unsigned char *signature = NULL;
! 1470: unsigned char *server_host_key_blob = NULL;
! 1471: unsigned int sbloblen;
! 1472: unsigned int klen, kout;
! 1473: unsigned char *kbuf;
! 1474: unsigned char *hash;
! 1475: BIGNUM *shared_secret = 0;
! 1476: DH *dh;
! 1477: BIGNUM *dh_client_pub = 0;
! 1478:
! 1479: /* KEXDHGEX */
! 1480: debug("Wait SSH2_MSG_KEX_DH_GEX_REQUEST.");
! 1481: packet_read_expect(&payload_len, SSH2_MSG_KEX_DH_GEX_REQUEST);
! 1482: nbits = packet_get_int();
! 1483: dh = choose_dh(nbits);
! 1484:
! 1485: debug("Sending SSH2_MSG_KEX_DH_GEX_GROUP.");
! 1486: packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
! 1487: packet_put_bignum2(dh->p);
! 1488: packet_put_bignum2(dh->g);
1.98 markus 1489: packet_send();
1490: packet_write_wait();
1491:
1.129 ! provos 1492: debug("Wait SSH2_MSG_KEX_DH_GEX_INIT.");
! 1493: packet_read_expect(&payload_len, SSH2_MSG_KEX_DH_GEX_INIT);
! 1494:
! 1495: /* key, cert */
! 1496: dh_client_pub = BN_new();
! 1497: if (dh_client_pub == NULL)
! 1498: fatal("dh_client_pub == NULL");
! 1499: packet_get_bignum2(dh_client_pub, &dlen);
! 1500:
! 1501: #ifdef DEBUG_KEXDH
! 1502: fprintf(stderr, "\ndh_client_pub= ");
! 1503: BN_print_fp(stderr, dh_client_pub);
! 1504: fprintf(stderr, "\n");
! 1505: debug("bits %d", BN_num_bits(dh_client_pub));
! 1506: #endif
! 1507:
! 1508: #ifdef DEBUG_KEXDH
! 1509: fprintf(stderr, "\np= ");
! 1510: BN_print_fp(stderr, dh->p);
! 1511: fprintf(stderr, "\ng= ");
! 1512: bn_print(dh->g);
! 1513: fprintf(stderr, "\npub= ");
! 1514: BN_print_fp(stderr, dh->pub_key);
! 1515: fprintf(stderr, "\n");
! 1516: DHparams_print_fp(stderr, dh);
! 1517: #endif
! 1518: if (!dh_pub_is_valid(dh, dh_client_pub))
! 1519: packet_disconnect("bad client public DH value");
! 1520:
! 1521: klen = DH_size(dh);
! 1522: kbuf = xmalloc(klen);
! 1523: kout = DH_compute_key(kbuf, dh_client_pub, dh);
! 1524:
! 1525: #ifdef DEBUG_KEXDH
! 1526: debug("shared secret: len %d/%d", klen, kout);
! 1527: fprintf(stderr, "shared secret == ");
! 1528: for (i = 0; i< kout; i++)
! 1529: fprintf(stderr, "%02x", (kbuf[i])&0xff);
! 1530: fprintf(stderr, "\n");
! 1531: #endif
! 1532: shared_secret = BN_new();
! 1533:
! 1534: BN_bin2bn(kbuf, kout, shared_secret);
! 1535: memset(kbuf, 0, klen);
! 1536: xfree(kbuf);
! 1537:
! 1538: /* XXX precompute? */
! 1539: dsa_make_key_blob(sensitive_data.dsa_host_key,
! 1540: &server_host_key_blob, &sbloblen);
1.98 markus 1541:
1.129 ! provos 1542: /* calc H */ /* XXX depends on 'kex' */
! 1543: hash = kex_hash_gex(
! 1544: client_version_string,
! 1545: server_version_string,
! 1546: buffer_ptr(client_kexinit), buffer_len(client_kexinit),
! 1547: buffer_ptr(server_kexinit), buffer_len(server_kexinit),
! 1548: (char *)server_host_key_blob, sbloblen,
! 1549: nbits, dh->p, dh->g,
! 1550: dh_client_pub,
! 1551: dh->pub_key,
! 1552: shared_secret
! 1553: );
! 1554: buffer_free(client_kexinit);
! 1555: buffer_free(server_kexinit);
! 1556: xfree(client_kexinit);
! 1557: xfree(server_kexinit);
1.100 markus 1558: #ifdef DEBUG_KEXDH
1.129 ! provos 1559: fprintf(stderr, "hash == ");
! 1560: for (i = 0; i< 20; i++)
! 1561: fprintf(stderr, "%02x", (hash[i])&0xff);
! 1562: fprintf(stderr, "\n");
! 1563: #endif
! 1564: /* save session id := H */
! 1565: /* XXX hashlen depends on KEX */
! 1566: session_id2_len = 20;
! 1567: session_id2 = xmalloc(session_id2_len);
! 1568: memcpy(session_id2, hash, session_id2_len);
! 1569:
! 1570: /* sign H */
! 1571: /* XXX hashlen depends on KEX */
! 1572: dsa_sign(sensitive_data.dsa_host_key, &signature, &slen, hash, 20);
! 1573:
! 1574: destroy_sensitive_data();
! 1575:
! 1576: /* send server hostkey, DH pubkey 'f' and singed H */
! 1577: packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
! 1578: packet_put_string((char *)server_host_key_blob, sbloblen);
! 1579: packet_put_bignum2(dh->pub_key); /* f */
! 1580: packet_put_string((char *)signature, slen);
1.98 markus 1581: packet_send();
1.129 ! provos 1582: xfree(signature);
! 1583: xfree(server_host_key_blob);
1.98 markus 1584: packet_write_wait();
1.129 ! provos 1585:
! 1586: kex_derive_keys(kex, hash, shared_secret);
! 1587: packet_set_kex(kex);
! 1588:
! 1589: /* have keys, free DH */
! 1590: DH_free(dh);
1.1 deraadt 1591: }
1.129 ! provos 1592:
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